9804327 Kumar The primary focus of this work is to establish the molecular bases for the miscibility of model polymer blends in the bulk and near surfaces. These issues are interesting and relevant since polymers used in practice are frequently blended to tune properties and the phase state of the resulting mixture plays a critical role in this context. The consequences of phase separation in a thin film on the nanostructure of flexible confining boundaries, such as the air surface, will also be studied in this work. This is practically important since the roughness of the air-polymer interface crucially affects the gloss of a coating film. The primary tools to be employed in this work are relatively novel scattering probes including small angle neutron scattering applied to ultrathin films and wide angle x-ray scattering and computer simulations. These methods, in combination with standard statistical mechanics, will be used to incisively establish the connection between the local structure of the molecules, local packing obtained from wide angle scattering and the macroscopic thermodynamics small angle scattering for the bulk and the confined systems. The approach outlined above is in contrast to most past work, which have treated the bulk and surface behavior as two separate problems. Consequently, very little molecular based understanding of these interrelated situations exists at this time. It is this void that the proposed work will fill. %%% The proposed work, which will utilize novel experimental and theoretical tools in an integrated fashion, will aid in the efficient design of polymeric materials with desired properties for use in practical applications, ranging from the ubiquitous e.g., packaging to "high-tech" e.g., lubricants for hard discs, adhesives . ***

National Science Foundation (NSF)
Division of Materials Research (DMR)
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Andrew J. Lovinger
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Pennsylvania State University
University Park
United States
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